During the past 1 1/2 years we have been making successful progress in characterizing the mechanical properties of lungs. We wish to continue our efforts during the next several years by applying principles of structural mechanics to study the nature and physiological implications of uneven stresses and deformations in normal and abnormal lungs, in particular to such problems as pleural pressure distribution as related to gravity, shape of chest cavity and lobation, the distribution of stresses around regions in the lung with non-homogeneous elasticity properties, and the variation of regional ventilation in lung in the gravity field. Three-dimensional experimental observations on lung tissue specimens were made (in collaboration with Dr. Fred Hoppin). A strain energy function describing the large deformation nonlinear elastic properties of lung parenchyma (based on the experimental results) has been successfully accomplished. Furthermore, finite element solution procedures to lung elasticity problems are being established. We are in a unique position to investigate the above mentioned lung elasticity problems and to begin examining the efforts of uneven stresses and deformation in the lung on the regional variations in ventilation and gas exchange. This latter study will be made in collaboration with Dr. Leon Farhi, Professor of Physiology, SUNY/Buffalo. Necessary experiments will be carried out in his Environmental Physiology Laboratory.